Iodes tubulifera Del Rio, Thomas & De Franceschi emend. Del Rio & De Franceschi

Rio, Cédric Del & Franceschi, Dario De, 2020, Icacinaceae fossil fruits from three sites of the Paris Basin (early Eocene, France): local diversity and global biogeographic implications, Geodiversitas 42 (2), pp. 17-28 : 22-23

Iodes tubulifera Del Rio, Thomas & De Franceschi emend. Del Rio & De Franceschi ( Fig. 3 )

EMENDED DIAGNOSIS. — Endocarp elliptical with a reticulate pattern of sharp and thin ridges, delimiting at least 21 polygonal areoles per face, with few or no freely ending ridgelets. Endocarp possessing a symmetrical pair of horn-like protrusions prominent from the keel, positioned eccentrically and subapically. Endocarp wall about 0.2 mm thick (excluding ridges, about 0.3 mm including ridges). Inner endocarp surface densely covered with regularly spaced, minute and tubular papillae. Length of the endocarp 8.8-11.2 mm. STRATIGRAPHY. — Late Paleocene.

ADDITIONAL STRATIGRAPHY. — Early Eocene.

TYPE LOCALITY. — Rivecourt (Oise, France).

ADDITIONAL LOCALITY. — Passy ( France).

SPECIMENS. — MNHN.F.44738 , MNHN.F.44740 .

DESCRIPTION (PASSY SPECIMENS).

Endocarp bilaterally symmetrical, unilocular, single-seeded, elliptical, laterally compressed in the plane of symmetry; length 8.8- 11.2 mm, width unknown (estimated about 6-7 mm), thickness 1.9 mm. Outer part of the endocarp with a reticulate pattern of sharp and thin ridges, with at least five irregular longitudinal ridges, delimiting at least 23 polygonal areoles per face with few or no freely ending ridgelets ( Fig. 3A, C ); a keel surrounds the fruit in the plane of symmetry, with the thicker margin containing a vascular bundle embedded in the endocarp wall and the other part thin ( Fig.3B ). Endocarp possessing a symmetrical pair of horn-like protrusions prominent from the keel, positioned eccentrically and subapically on the apical endocarp faces, each with a central pit ( Fig. 3A, C, D ); Endocarp wall 0.2-0.23 mm thick excluding ridges, (0.3-0.33 mm including ridges, Fig.3G ). Wall composed of four units of one or several successive cell rows, the outermost corresponding to an apical sclerotic row, cells difficult to distinguish, sometimes absent by erosion on the areoles, which shows the isodiametric unistratified cell row, cells 0.034 -0.053 mm diameter. The basal sclerotic row forming the major part of the endocarp wall thickness is composed of 6-8 sclerotized and periclinal cell rows 0.010 -0.013 mm high, 0.030 - 0.041 mm wide. Inner endocarp surface densely covered with regularly spaced, minute and tubular papillae (cell expansion of the locule epiderma layer); papillae diameter 0.018 -0.020 mm, about 290 papillae per 0.25 mm ² ( Fig. 3H, I ).

SYSTEMATIC AFFINITY

These two specimens correspond in almost all characters to the specimens of Iodes tubulifera from Rivecourt site. In particular, the presence of characteristic tubular and sparse papillae is strong evidence for this affinity. Here, the density is c. 290 papillae per 0.25 mm 2 whereas the density of I. tubulifera specimens from Rivecourt is c. 270 papillae per 0.25 mm 2. We think that differences of only 20 papillae per 0.25 mm 2 could be due to taphonomic processes or natural range of variation for this species. The sharp ridges and the size of the specimen here support this species assignment. In fact, the sharp ridges are very similar in shape and only slightly higher in the new specimens presented here. The endocarp wall is also very similar in all aspects. The size of the specimens presented here brackets the values of the specimen from Rivecourt. Therefore, we have sufficient justification to attribute these specimens to I. tubulifera .

Figures

FIG. 3. — A-E, Iodes tubulifera Del Rio, Thomas & De Franceschi (MNHN.F.44738): A, lateral view of an endocarp showing the reticulum pattern of sharp ridges; B, dorsal view showing the keel; C, lateral view of second face of the endocarp; D, apical view showing the small pair of horns (arrows); E, basal view. F-I, MNHN.F.44740; F, lateral view of the endocarp showing the reticulum pattern of sharp ridges; G, SEM view of the endocarp wall units and ridges in transversal section; H, SEM view of tubular papillae; I, same with magnification. Scale bars: A-F, 5 mm; G-H, 500 µm; I, 30 µm.